WASHINGTON - An international team of researchers have announced the discovery of 104 new planets outside our solar system,including four that could have Earth-like, rocky surfaces.

Scientists on Monday discovered the exoplanets using the Kepler space telescope aswell as ground observations by Earth-based telescopes, including four on thesummit of Mauna Kea in Hawaii.

The US$600 million Kepler mission has allowed scientists to discover morethan 4,600 planets -- 2,326 of them confirmed -- since it launched in 2009.

"The diversity of planets is astounding," said Evan Sinukoff, an astronomerat the University of Hawaii who contributed to the research.

"We discovered many planets about twice the size of the Earth orbiting soclose to their host stars that they are hotter than 1000 degrees."

The latest trove includes 21 situated within their sun’s habitable zone --the distance from a star that could permit liquid water to exist and supportlife.

The four potentially rocky planets -- ranging from 20 to 50 percent largerthan Earth -- orbit tightly around the same star in a planetary system about400 light-years from Earth.

Though the planets rotate around their star even closer than Mercury orbitsthe sun, two of the planets may have surface temperatures similar to Earth’s,as their star is cooler than our sun, astronomers said.

The unmanned Kepler mission has been scanning 150,000 stars in the Cygnusconstellation for signs of orbiting bodies, particularly those that might beable to support life.

It works by observing a dimming in the light of a star, known as a transit,each time an orbiting planet passes in front of it.

In 2013, the space telescope suffered a problem with the reaction wheelsthat typically keep the spacecraft steady.

NASA subsequently set the spacecraft on a new mission called K2, to studysupernovas, star clusters and far-off galaxies.

Scientists verified the latest exoplanets as part of the K2 mission. – AFP